black walnut

description
Black walnut, a flowering tree in the Juglandaceae family, can grow up to 150 feet in height.

The bark is black, thick and deeply furrowed. When scraped with a knife, it reveals a chocolate-covered sub-surface. The twigs are stout, greenish or orange-brown in color, and may be hairy or smooth. The pith is dark brown in color and is partitioned when sliced with a knife. The leaves are alternate and pinnately compound. When crushed, the leaves have a distinct "walnut" smell.

The flowers are borne separately, but on the same tree. They appear as yellow-green catkins, and appear when the leaves are partly grown. The staminate (males), are most abundant and are thicker when compared to the pistillates (females), which are fewer in number and smaller. The flowers have no petals.

The fruits (walnuts) occur singly or in groups of 2 or 3. They are spherical in shape and 2 inches or larger in diameter. The outer husk is yellow-green, but quickly darkens and turns black when they fall to the ground. The inner nut has a very hard shell, is dark brown in color, deeply ridged and has a sweet tasting edible nut.

common names
& nomenclature
Juglans comes from the Latin words jovis and glans meaning nut of Jove. Nigra means black, in reference to the dark bark and nuts.

Also known as:
black walnut, american walnut, eastern black walnut, carya, carya basilike, carya persica, green black walnut, green walnut, juglans nigra, jupiter's nuts, nogal americano, nogal negro, nogueira-preta, noix, noix de jupiter, noix de perse, noix verte, noyer d'amérique, noyer noir, noyer noir américain, nux persica, nux regia, schwarze walnuss, walnoot, and walnut

climate
Black walnut grows best in full sun.

soil
Black walnut requires well-drained soil that has a neutral pH. Poorly draining soil may lead to root rot, which is a condition that deteriorates the structure and function of the plants root system. Black walnut trees thrive in rich loamy or sandy soil.

growing
The best way to propagate this plant is by sowing seeds. Collect the nuts and plant in moist, well-drained, rich soil during the fall or spring after a cold stratification of 90-120 days. It is recommended to remove the husk.

Seedlings emerge in April or May the first or second spring after the seed is planted. Although young trees will sometimes begin producing nuts when only 4-6 years old, it usually takes 20 years before a tree will produce a large crop of nuts.

harvesting
As black walnuts ripen, the husk changes from solid green to yellowish green. Walnut juice leaves a dark stain, so wear gloves when you handle unhusked walnuts. Press on the skin of the walnut with your thumb; ripe nuts will show an indentation. Weekly monitoring is important as nuts will mature over a four to six week period. Try to harvest the ripe nuts directly from the tree, ahead of the squirrels. If the nuts are too difficult to reach, they can be collected after they fall from the tree during frosts. Often the husk of mature nuts has dried and cracked. Husks must be removed before you store black walnuts.

preserving
Hulling walnuts, removing the husk, must be done prior to storage and can be a difficult and messy task. The indelible dye from the husk stains hands, clothes, tools and work surfaces. If you are working with dry nuts, the husk can be removed by applying pressure to the ends of the nut. This can be done by pounding side to side with a hammer, of course while wearing safety glasses.

The husks can also be softened in a container filled with a slurry of three parts nuts to one part water and a handful of gravel. Stir the mixture vigorously. It may take more than one attempt to completely remove the husks. If you are hulling a large quantity of nuts, the slurry can be used in a small portable cement mixer.

After hulling, wash the unshelled nuts. After husks have been removed, the nuts must be cured. Curing prepares the walnuts for storage and allows the walnut flavor to develop. To cure black walnuts, stack the clean hulled nuts in shallow layers only two or three nuts deep. Place the nuts in a cool, dry, well-ventilated area out of direct sunlight for two weeks.

To be certain nuts have cured adequately, break open a sample nut. When the nut is dry enough to store, its kernel will break crisply, with a sharp snap. If cured improperly, nuts will mold.

After curing, store unshelled nuts in a well-ventilated area at 60°F or less. Cloth bags or wire baskets allow adequate air circulation and discourage development of mold. Try to keep the relative humidity fairly high, ideally about 70%. Nut shells will crack and the kernels spoil if nuts are stored in too dry an area.

When you're ready to shell the nuts, moisten them to keep the kernels from shattering. Soak the walnuts in hot tap water for about 24 hours. Drain and replace the hot water and soak the nuts for two more hours. Cover the nuts with moist cloths until you're ready to crack the shells.

After shelling, nut meats can be stored in several ways: at room temperature, refrigerated or frozen. If you plan to store the nutmeats in a container at room temperature and use them within a few weeks, first bake them at 215° for 10 to 15 minutes. Nutmeats can be refrigerated in a jar or plastic bag for up to nine months without baking. Nutmeats can also be frozen for longer term storage, but use them within two years.

Black walnut (Juglans nigra) is a North American flowering tree that is related to the hickory. Dendrologists, and others who fancy deciduous plants and trees, appreciate the fact that these stately giants are outstanding shade providers. However, there is a long-standing belief that black walnut trees also protect the home from lightning strikes. While some believe this is due to the presence of an abundance of minerals in the timber that act as electrical conductors, it may also be due to the fact that mature black walnut trees can reach up to 60 feet in height. Whatever the reason, these trees have apparently saved many abodes from disaster since it was once commonplace to adopt a strategy of planting groves of them in proximity. In fact, the next time you visit a historic residence or farmstead, conduct a visual scan of the property. Chances are you’ll see several black walnut trees standing ready to deter misfortune. As an added bonus, early homesteaders knew that the presence of black walnut on a potential stake of property indicated that the land was fertile since these trees require a rich, slightly alkaline, and well-drained soil in order to thrive.

The hardwood of black walnut is highly valued for its exceptional beauty and durability. The wood is particularly dense, yet it splits readily and is easier to machine than many other types of wood. These qualities have inspired seafarers, gun manufacturers, and undertakers to use the wood to make boats, gunstocks, and coffins from the wood.

Of course, many specimens of fine antique furniture are also made of this material. In fact, until mahogany came into fashion in the late 18th century, black walnut was the wood of choice of furniture makers. During World War I, the husks of the tree were used to produce a high-grade charcoal to filter gas masks. In the mid-20th century, various parts of the tree were used to make an insecticide and herbicide, the effectiveness of which was owing to the presence of juglone.

Juglone, chemically known as 5-hydroxy-alphanapthaquinone, is classified an allelochemical, meaning that it negatively affects the growth of certain neighboring plants by impairing enzymatic processes necessary for survival. This is why some gardeners consider black walnut to be a hindrance in terms of limiting options in landscaping. Regardless, juglone is potent stuff. It's the reason that black walnut trees are rarely impacted by disease and explains why insects won’t even come into contact with the leaves.